The invention pertains to protective devices for tubular goods and more particularly to increased tensile strength variable diameter protective joints for use as so called blast joints with oil well production tubing.
In oil and gas wells the flow of gas, oil, fluids or combinations thereof from perforations in an underground pressure source often entrains solids including grains of sand. The resulting flow of gas or oil entrained solids often has a sufficient abrasive or cutting effect to cut holes into metal production tubing.
Through the use of logs and other methods well operators are able to locate the perforations in relation to a production tubing string, particularly since the perforations are generally man made. However, exact location of perforations in relation to the production string may be difficult due to the number of variables involved, including the length and weight of the production string, the configuration of the hole, and conditions downhole, such as temperature.
Through the years a number of so called blade joints have been developed with a view toward protecting production tubing. A number of patents disclose a variety of blast joints for tubulars. For example, Duesterberg, U.S. Pat. No. 2,925,097, discloses a covered tubular member for positioning in a well flow pipe. A tubular member is provided with a covering which is said to protect the tubular member from the cutting action of well fluids. The covering includes a coating of a resilient material which may be arranged on the outer surface of the tubular member in strip form. A sleeve formed of hard, brittle material covers the surface of the tubular member between two collars. The collars are adjacent to each end of the tubular member. The sleeve may be formed by a plurality of tubular members which are said to be in end to end interfitting or overlapping relation. Each of the plurality of tubular members forming the sleeve may be provided with recessed portions for interfitting and overlap. A second layer of resilient material is provided on substantially all of the outer surface of the sleeve to act as a shock absorber to protect the sleeve from breakage or damage as the tubular member and connected pipe sections are lowered into position in the well bore. In order to further protect the sleeve an outer shell of metal may be provided which extends between the collars and is secured to each collar by welding.
Ribb, U.S. Pat. No. 3,382,930, discloses a blast joint employing a ceramic material said to resist the eroding action of a fluid flowing against the joint. As disclosed therein, the blast joint includes a ceramic sleeve made up of a plurality of tubular ceramic members that are slipped on a tubing joint in end to end relationship. The ceramic members are held in position by annular collars of an impact resistant, non-brittle material, such as steel. They are provided with a plurality of set screws which engage the tubing joint and hold the collars and the ceramic members between them against longitudinal movement on the joint. The annular collars are spaced from the ends of the tubing joint. A protector made up of an annular ring is located in a groove on the exterior of the blast joint and encircles it to prevent the blast joint from hanging upon obstructions in the well bore. Means are also provided as a cushion between ceramic members and means for holding the members spaced from the tubing string.
Bergstrom, U.S. Pat. No. 4,349,050, which has a common assignee with this invention, discloses a blast joint for subterranean wells. The blast joint is positioned around a section of production tubing. A plurality of rings are assembled on the section of production tubing in end face-to-face array. These rings fit snugly on the production tubing and are formed of a very hard and abrasive resistant material. The ends of the rings are lap finished and the assembly is maintained on the compression by end collars and wave spring washers. When the blast joint is to extend the distance greater than a single section of tubing, two segments of production tubing are prepared by cutting the pin and box end from respective lengths of the production tubing. The resultant segments are joined in a flush pin and box joint.
Other patents assigned to the same assignee as this invention disclose blast joints comprising a plurality of rings. These include U.S. Pat. No. 4,141,386, entitled Blast Joint; U.S. Pat. No. 4,028,796, entitled Method of Making a Blast Joint; and U.S. Pat. No. 4,211,440, entitled Compensated Blast Joint for Oil Well Production Tubing.
Prior devices suffer from one or more of several difficulties or limitations including difficulties or limitations in handling, shipping, manufacturing, assembly, overall effectiveness, longevity, and reusability. Many of these problems are addressed by one or more of the inventions previously assigned to the same assignee as this invention. However, prior devices still suffer from a limitation in not being able to directly and as effectively protect both the tubular and an increased diameter portion of the tubular such as collars used with external non-upset tubing and upset tubing. Further, prior devices have been unable to provide as effective a protective device covering a plurality of tubulars, such as oil well tubing, without impairing the tensile strength of the tubing string. These and other problems encountered with prior devices as alleviated if not substantially eliminated by the present invention.